Over-the-air calibration of antenna system

ABSTRACT

In an embodiment, an apparatus includes a first baseband section to receive a calibration signal; a first radio frequency (RF) section configured to generate a RF calibration signal based on modulating the calibration signal. The calibration signal comprises an orthogonal code based signal. The apparatus includes a second RF section to receive the RF calibration signal and generate a received calibration signal based on demodulating the RF calibration signal; a calibration section; a first antenna electrically coupled to the first RF section and configured to transmit the RF calibration signal; and a second antenna electrically coupled to the second RF section and configured to receive the RF calibration signal. The calibration section is configured to determine one or more of gain, baseband delay, or RF delay to calibrate the first RF section; and the second antenna is switchable between receiving the RF calibration signal and transmitting an encoded data signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 17/747,895, filed May 18, 2022, entitled OVER-THE AIRCALIBRATION OF ANTENNA SYSTEM, which is a continuation of U.S. patentapplication Ser. No. 15/931,443 filed May 13, 2020, now U.S. Pat. No.11,362,742, issued Jun. 14, 2022, entitled OVER-THE AIR CALIBRATION OFANTENNA SYSTEM which claims priority to U.S. Provisional PatentApplication No. 62/847,873 filed May 14, 2019, entitled ANTENNACALIBRATION, the disclosures all of which are hereby expresslyincorporated by reference in their entirety.

BACKGROUND

An antenna (such as a dipole antenna) typically generates radiation in apattern that has a preferred direction. For example, the generatedradiation pattern is stronger in some directions and weaker in otherdirections. Likewise, when receiving electromagnetic signals, theantenna has the same preferred direction. Signal quality (e.g., signalto noise ratio or SNR), whether in transmitting or receiving scenarios,can be improved by aligning the preferred direction of the antenna witha direction of the target or source of the signal. However, it is oftenimpractical to physically reorient the antenna with respect to thetarget or source of the signal. Additionally, the exact location of thesource/target may not be known. To overcome some of the aboveshortcomings of the antenna, a phased array antenna can be formed from aset of antenna elements to behave as a large directional antenna. Anadvantage of a phased array antenna is its ability to transmit and/orreceive signals in a preferred direction (e.g., the antenna'sbeamforming ability) without physical repositioning or reorientating.

It would be advantageous to configure phased array antennas havingincreased bandwidth while maintaining a high ratio of the main radiatedlobe power to the side lobe power. Likewise, it would be advantageous toconfigure phased array antennas and associated circuitry having reducedweight, reduced size, lower manufacturing cost, and/or lower powerrequirements. It would be advantageous to maintain the phased arrayantennas and associated circuitry in a nominal or narrow operatingrange. Accordingly, embodiments of the present disclosure are directedto these and other improvements in phased array antennas or portionsthereof.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is an example illustration of a block diagram showingover-the-air calibration components in connection with transmit sectioncalibration in accordance with various aspects of the presentdisclosure.

FIG. 2 is an example illustration of a block diagram showingimplementation of an intra-chip transmit calibration scheme inaccordance with various aspects of the present disclosure.

FIG. 3 is an example illustration of a block diagram showingimplementation of an inter-chip transmit calibration scheme for a samesubset or cluster of antenna elements in accordance with various aspectsof the present disclosure.

FIG. 4 is an example illustration of a block diagram showingimplementation of an inter-chip transmit calibration scheme involvingtwo subsets or clusters of antenna elements in accordance with variousaspects of the present disclosure.

FIG. 5 is an example illustration of a top view of an antenna lattice ofa phased array antenna in accordance with various aspects of the presentdisclosure.

FIG. 6A illustrates a block diagram showing example modules ofcorrelators and least means square (LMS) engine configured to perform anover-the-air calibration technique in accordance with various aspects ofthe present disclosure.

FIG. 6B illustrates a flow diagram showing a process to calibrate atransmit section and associated antenna element using the over-the-aircalibration technique in accordance with various aspects of the presentdisclosure.

FIG. 7A illustrates an example block diagram showing gain and delaycompensator(s) included in a transmit section of interest in accordancewith various aspects of the present disclosure.

FIG. 7B illustrates an example block diagram showing gain and delaycompensator(s) included in a receive section of interest in accordancewith various aspects of the present disclosure.

FIG. 8 is an example illustration of a block diagram showing integratedcircuit (IC) chips and associated antenna elements in accordance withvarious aspects of the present disclosure.

FIG. 9 is an example illustration of a block diagram showingover-the-air calibration components in connection with receive sectioncalibration in accordance with various aspects of the presentdisclosure.

FIG. 10A illustrates a block diagram showing example modules ofcorrelator(s) and LMS engine configured to perform an over-the-aircalibration technique in accordance with various aspects of the presentdisclosure.

FIG. 10B illustrates a flow diagram showing a process to calibrate areceive section and associated antenna element using the over-the-aircalibration technique in accordance with various aspects of the presentdisclosure.

FIG. 11 illustrates a block diagram showing an example platform ordevice that can be implemented in at least a portion of the calibrationreceive sections and/or calibration transmit sections in accordance withvarious aspects of the present disclosure.

DETAILED DESCRIPTION

Embodiments of apparatuses and methods relate to over-the-aircalibration techniques to compensate for gain and delay offsetsassociated with antennas and associated transmission or receivecircuitry. In an embodiment, an apparatus is included in acommunications system, the apparatus including a transmit sectionincluding a first baseband section and a first radio frequency (RF)section, wherein the transmit section is configured to receive acalibration signal, the first RF section is configured to generate a RFcalibration signal based on modulating the calibration signal, whereinthe calibration signal comprises an orthogonal code based signal; and areceive section configured to receive the RF calibration signalover-the-air, wherein the receive section includes a second RF sectionand a calibration section, wherein the second RF section is configuredto generate a received calibration signal based on the RF calibrationsignal, wherein the received calibration signal and a reference signalassociated with the RF calibration signal comprise inputs to thecalibration section, and the calibration section is configured todetermine one or more of gain, baseband delay, or RF delay compensationvalues, based on the inputs, to calibrate the transmit section. Theseand other aspects of the present disclosure will be more fully describedbelow.

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will be describedherein in detail. It should be understood, however, that there is nointent to limit the concepts of the present disclosure to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives consistent with the presentdisclosure and the appended claims.

References in the specification to “one embodiment,” “an embodiment,”“an illustrative embodiment,” etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may or may not necessarily includethat particular feature, structure, or characteristic. Moreover, suchphrases are not necessarily referring to the same embodiment. Further,when a particular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to affect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described. Additionally, it should be appreciated that itemsincluded in a list in the form of “at least one A, B, and C” can mean(A); (B); (C); (A and B); (B and C); (A and C); or (A, B, and C).Similarly, items listed in the form of “at least one of A, B, or C” canmean (A); (B); (C); (A and B); (B and C); (A and C); or (A, B, and C).

Language such as “top surface,” “bottom surface,” “vertical,”“horizontal,” and “lateral” in the present disclosure is meant toprovide orientation for the reader with reference to the drawings and isnot intended to be the required orientation of the components or toimpart orientation limitations into the claims.

In the drawings, some structural or method features may be shown inspecific arrangements and/or orderings. However, it should beappreciated that such specific arrangements and/or orderings may not berequired. Rather, in some embodiments, such features may be arranged ina different manner and/or order than shown in the illustrative figures.Additionally, the inclusion of a structural or method feature in aparticular figure is not meant to imply that such feature is required inall embodiments and, in some embodiments, it may not be included or maybe combined with other features.

Many embodiments of the technology described herein may take the form ofcomputer- or controller-executable instructions, including routinesexecuted by a programmable computer or controller. Those skilled in therelevant art will appreciate that the technology can be practiced oncomputer/controller systems other than those shown and described above.The technology can be embodied in a special-purpose computer, controlleror data processor that is specifically programmed, configured orconstructed to perform one or more of the computer-executableinstructions described above. Accordingly, the terms “computer” and“controller” as generally used herein refer to any data processor andcan include Internet appliances and hand-held devices (includingpalm-top computers, wearable computers, cellular or mobile phones,multi-processor systems, processor-based or programmable consumerelectronics, network computers, mini computers and the like).Information handled by these computers can be presented at any suitabledisplay medium, including an organic light emitting diode (OLED) displayor liquid crystal display (LCD).

FIG. 1 is an example illustration of a block diagram showingover-the-air calibration components in connection with transmit sectioncalibration in accordance with various aspects of the presentdisclosure. In some embodiments, actual time delay, phase, and amplitudeof a reference signal transmitted by an antenna element included in aphased array antenna can be measured. This is accomplished by a receiveantenna and a calibration receiver, and then the received signal iscorrelated with the reference signal. Based on the measured time delay,phase, and/or amplitude, the transmitter from which the reference signalwas transmitted is compensated in order to improve the radiatedperformance of the phased array antenna (e.g., main beam direction andside lobe level). Phase accuracy achieved from the over-the-aircalibration technique disclosed herein is in the range of asub-picosecond at the actual operating radio frequency (RF) frequency.

Each antenna element of the phased array antenna and its associatedtransmission or receiver circuity undergoes a similar calibration. Suchmeasurements and calibration based on the measurements can be performedsimultaneously with or independent of normal operation of the phasedarray antenna (e.g., during transmission and receiving of regular ornormal signals in the phased array antenna). In some embodiments,signal-to-noise (SNR) conditions are taken into account in performanceof over-the-air calibration by using clusterizaton.

In some embodiments, the configuration of FIG. 1 is associated withcalibrating a transmit section 102 using a waveform generator 101 and acalibration receive section 104 in accordance with a calibrationtechnique disclosed herein. The waveform generator 101 is electricallycoupled to each of the transmit section 102 and the calibration receivesection 104. Transmit section 102 comprises the signal processingcomponents that configure data to be transmitted into a format where atleast a portion of the data can be transmitted by an antenna element 124to be recovered by a destination receiver. Calibration receive section104 can also receive the signal transmitted through (transmit) antennaelement 124 via (receive) antenna element 134. Antenna elements 124 and134 are included in the same phased array antenna panel. In someembodiments, antenna element 134 can be configured to act as a receiveantenna element for calibration receive section 104 during calibrationand as another transmit antenna element, along with antenna element 124,in the phased array antenna when calibration is not being performed.

A plurality of transmit sections similar to transmit section 102 andassociated antenna elements collectively transmit the data in itstotality, in some embodiments. A signal processing pathway or path i isdefined by the components of transmit section 102 and is associated withan ith antenna element. Transmit section 102 comprises the ith path forthe ith antenna element 124.

Transmit section 102 includes, without limitation, a baseband processingsection 106 and a radio frequency (RF) section 112. Baseband processingsection 106, also referred to as a baseband section 106, is configuredto encode or perform beamforming on data signal 150 to be transmitted.Data signal 150 to be transmitted is also referred to as a datawaveform, a data stream, a data beam, data, and/or the like. Data signal150 comprises a normal or regular signal that is to be transmittedduring normal operation of the antenna element 124 and transmit section102. Data signal 150 is provided by a modem. In the case of multi-beamoperation, multiple data streams such as data signal 150 are received bybaseband section 106 from one or more modems. Each data stream of themultiple data streams is time and phase encoded independently of eachother and then combined before passing to RF section 112.

Time delay filter(s) 108 is configured to encode the data signal 150with particular time delay(s), and the phase shifter(s) 110 isconfigured to encode the data signal 150 with particular phase(s).Transmit section 102 may also be referred to as a transmitter,transmitter section, and/or the like.

The time delay and phase encoded (digital) data signal, also referred toas a baseband signal, comprises the input to the RF section 112. The RFsection 112 includes, without limitation, a transmit digital front end(Tx DFE) 114, a digital-to-analog converter (DAC) 116, a low pass filter(LPF) 118, a mixer 120, and a power amplifier (PA) 122. RF section 112is also referred to as a modulation section. The Tx DFE 114 receives thetime delay and phase encoded digital data signal. Tx DFE 114 isconfigured to be a bridge between the baseband processing in section 106and the analog RF processing to be performed in the RF section 112. TxDFE 114 may be responsible for one or more processing functions relatedto channelization, channel bonding, and/or sample rate conversion. TxDFE 114 is configured to, among other things, resample the digitalsignal to a higher sample rate or density and provide the up sampledsignal to the DAC 116.

DAC 116 is configured to convert the digital signal into an analogsignal. DAC 116 may comprise an IQ DAC. The time delay and phase encodeddigital data signal is now a time delay and phase encoded analog signal.The analog signal is the input to LPF 118.

LPF 118 is configured to low pass filter or de-noise the analog signal.The filtered analog signal is the input to mixer 2120. Mixer 120 isconfigured to perform frequency up conversion to convert the basebandfrequency associated with the filtered analog signal to a carrierfrequency (e.g., change from f_(DC) to f_(RF)). Although not shown, asignal from a local oscillator is also an input to mixer 120 in order toperform the frequency up conversion. The time delayed and phase encodedanalog signal provided on a carrier frequency, also referred to as a RFsignal, is power amplified by the PA 122.

The amplified RF signal outputted by the PA 122 is the input to theantenna element 124. In turn, the antenna element 124 radiates theamplified RF signal. In some embodiments, PA 122 may comprise apre-power amplifier (PPA) and another PA may be provided external totransmit section 102 between PA 122 and antenna element 124. In someembodiments, a bandpass filter may be electrically coupled between thePA 122 and antenna element 124.

A reference waveform 152 is generated by the waveform generator 101 andprovided to transmit section 102. The reference waveform 152 comprisesan orthogonal code based signal such as, but not limited to, a codedivision multiple access (CDMA) signal. Reference waveform 152 is alsoreferred to as a reference signal, a calibration waveform, a calibrationsignal, a calibration reference signal, a calibration referencewaveform, and/or the like.

In some embodiments, the reference waveform 152 is duplexed or combinedwith the time delay and phase encoded (digital) data signal (the datasignal 150 processed by baseband section 106 and to be provided to theRF section 112) by a duplexer 111 included in the baseband section 106.Unlike the data signal 150, reference waveform 152 is not processed orencoded by baseband section 106. The combined signal comprises the inputto RF section 112. RF section 112 processes the combined signal andoutputs a combined RF signal that is transmitted or radiated by antennaelement 124. When the transmitted combined RF signal is received by thecalibration receive section 104, the received signal portioncorresponding to the data signal 150 (the regular encoded signal) willbe considered noise relative to the received signal portioncorresponding to the reference waveform 152 (the non-encoded, knownreference signal). Using the combined signal, calibration of antennaelement 124 and/or transmit section 102 can be performed during normaloperation of antenna element 124 and/or transmit section 102.

Alternatively, data signal 150 can be optional and the referencewaveform 152 alone is transmitted by the antenna element 124. Referencewaveform 152 bypasses processing in baseband section 106 (e.g.,reference waveform 152 is not phase nor time delay encoded) and stillundergoes processing in the RF section 112 (e.g., conversion to ananalog signal, low pass filtered, up conversion, RF amplification,etc.). The resulting signal transmitted to calibration receive section104 comprises a reference RF signal.

The amplified RF signal transmitted by antenna element 124 (the combinedRF signal or the reference RF signal) is detected by an antenna element134 electrically coupled with the calibration receive section 104.Antenna element 134 is also referred to as a calibration antennaelement. While antenna element 124 comprises an antenna element that isused for normal or regular signal transmission as well as forcalibration purposes as described herein, antenna element 134 comprisesan antenna element dedicated for calibration purposes and/or an antennaelement switchable between calibration or regular signal transmissionpurposes. Antenna elements 124 and 134 can be included in the sameantenna lattice, as will be discussed in detail below.

Calibration receive section 104 includes, without limitation, a RFattenuator (Att) 136, a mixer 138, a low pass filter (LPF) 140, ananalog-to-digital converter (ADC) 142, and a receive digital front end(Rx DFE) 144. RF attenuator 136 is configured to adjust the level ofanalog RF signal received at antenna element 134 and to maintainoperation in linear mode, particularly for amplitude measurement. Theattenuated RF signal is the input to the mixer 138. A signal generatedby a local oscillator (not shown) is also an input to the mixer 138.Mixer 138, also referred to as a down converter, is configured toperform frequency down conversion to change the frequency associatedwith the attenuated RF signal from the RF carrier frequency to thebaseband frequency (e.g., change from f_(RF) to f_(DC)). Next, thesignal is low pass filtered or de-noised by LPF 140. The filteredsignal, which is an analog signal, is converted to a digital signal byADC 142. ADC 142 may comprise an IQ ADC. The output of ADC 142 is theinput to Rx DFE 144.

Calibration receive section 104 may also be referred to as a calibrationreceiver, an auxiliary receiver, a receiver, a receiver section, and/orthe like.

Rx DFE 144 is configured to perform one or more processing functionsrelating to channelization and/or sample rate conversion. Rx DFE 144 isconfigured to, among other things, resample the inputted digital signalto a lower sample rate or density or otherwise provide the digitizedsignal into a format suitable for calibration-related determinations.

Rx DFE 144 includes, without limitation, correlators 146 and 148 and aleast mean square (LMS) engine 160. Correlators 146, 148 are configuredto calculate correlations between the signal received by antenna element134 (e.g., the output of ADC 142) and a known signal from waveformgenerator 101 or baseband section 106. LMS engine 160 is configured toperform calculations to determine, based on the correlationdeterminations from correlators 146 and/or 148, the calibration to applyto calibrate transmit section 102.

In some embodiments, correlator 146, correlator 148, and/or LMS engine160 comprises hardware, firmware, circuitry, software, and/orcombinations thereof to facilitate various aspects of the calibrationtechniques described herein. Correlator 146, correlator 148, and/or LMSengine 160 may also be referred to as modules, logic, instructions,algorithms, and/or the like.

One or more of correlator 146, correlator 148, and/or LMS engine 160 (ora portion thereof) comprises one or more instructions embodied within atangible or non-transitory machine (e.g., computer) readable storagemedium, which when executed by a machine causes the machine to performthe operations described herein. One or more processors, controllers,microcontrollers, microprocessors, and/or the like included incorrelator 146, correlator 148, LMS engine 160, Rx DFE 144, section 104,external to Rx DFE 144, external to section 104, included in the samechip as section 104, and/or external to the chip which includes section104 can be configured to execute the instructions.

In an embodiment, one or more of correlator 146, correlator 148, and/orLMS engine 160 (or a portion thereof) can be implemented as firmware orhardware such as, but not limited to, an application specific integratedcircuit (ASIC), programmable array logic (PAL), field programmable gatearray (FPGA), and/or the like. In other embodiments, one or more ofcorrelator 146, correlator 148, and/or LMS engine 160 (or a portionthereof) may be implemented as software while other of the correlator146, correlator 148, and/or LMS engine 160 (or a portion thereof) may beimplemented as firmware and/or hardware.

Reference waveform 152 generated by waveform generator 101 can beprovided to both transmit section 102 and calibration receive section104. Provision of reference waveform 152 to calibration receive section104 may be possible if waveform generator 101 and calibration receivesection 104 are both located in the same IC chip, package, or device,for example. In some embodiments, a reference waveform 154 can beprovided by baseband section 106 (or more generally, transmit section102) to calibration receive section 104. Reference waveform 154comprises the output of baseband section 106. As described above, theoutput of baseband section 106 comprises the combined signal (e.g.,combination of encoded data signal and the unchanged reference waveform152 to be provided as the input to RF section 112), if data signal 150is also an input to baseband section 106 and is combined with thereference waveform 152, or the reference waveform 152 (e.g., referencewaveform 152 after traversal through baseband section 106 withoutprocessing or change), if no data signal 150 is available or data signal150 is not combined with reference waveform 152. Reference waveform 154comprises a feedback from transmit section 102. Reference waveform 154can be provided to calibration receive section 104 if both of thetransmit section 102 and calibration receive section 104 are included inthe same IC chip, package, or device, for example.

Reference waveform 152 and reference waveform 154 as received bycalibration receive section 104 basically comprise the same signal (orprovide the same signal information). Reference waveform 152 and/orreference waveform 154 received by calibration receive section 104 isalso referred to as a known signal, calibration signal, known waveform,known reference signal, reference signal, and/or the like.

In some embodiments, availability of one of reference waveform 152 or154 at calibration receive section 104 is sufficient for performance ofthe calibration technique disclosed herein. Correlator 146 and/or 148 isconfigured to calculate or determine correlations between the knownsignal (e.g., received reference waveform 152 and/or reference waveform154) and the output of ADC 142 (e.g., the received over-the-aircalibration signal after RF processing by components 136-142). Thecorrelation is between the non-encoded known signal and the non-encodedknown signal after traversal through the transmit section of interest(e.g., transmit section 102 to be calibrated), propagation over-the-air,and receipt by the calibration receive section 104.

The LMS engine 160 is configured to determine, based on thecorrelations, what calibration to apply to the transmit section 102 inorder to calibrate or pre-compensate for phase, time delay, and/oramplitude offset caused to one or more portions of the transmit section102, antenna element 124, coupling between antenna element 124 and oneor more other antenna elements of the phased array antenna,environmental conditions, wear and tear of components along thetransmission signal path, and/or other sources of phase, time delay,and/or amplitude offset between the known signal into transmit section102 and receipt of the known signal by calibration receive section 104.Phase is also referred to as RF delay or RF time delay. Time delay isalso referred to as baseband delay or baseband time delay. Amplitude isalso referred to as gain.

The correlations comprise initial or starting values from whichiterative calculations can be performed to determine the particularcalibration to be applied to transmit section 102, as will be describedin detail below.

In some embodiments, phase, time delay, and/or amplitude offset canoccur after an antenna system has been fully calibrated prior to startof normal operations. The full calibration prior to start of normaloperations comprises using individual probe measurements,processing-intensive computations, and setting of electrical componentsincluded in the antenna system based on the measurements andcomputations. Such full calibration scheme is referred to as park andmeasurement, park and measurement calibration, and/or the like. Duringnormal operation, park and measurement calibration may not be possible.Thus, the over-the-air calibration technique disclosed herein can beused to identify and appropriately compensate for phase, time delay,and/or amplitude offsets that occur after (or in between) park andmeasurement. Such offsets comprise deviations from the particular phase,time delay, and amplitude settings associated with electrical componentsfrom park and measurement. At least some of the deviations from park andmeasurement can be due to temperature variations during normaloperation.

One or both of antenna elements 124, 134 comprises part of one or morephased array antennas. Alternatively, at least one of antenna elements124, 134 can comprise a single antenna, such as a parabolic antenna.

In FIG. 1 , a single reference waveform 152 is used to calibrate asingle transmit section 102 using a single calibration receive section104. Such calibration scheme can be used to sequentially calibraterespective transmit sections included in a communications system. Insome embodiments, more than one transmit section can be simultaneouslycalibrated using one or more calibration receive sections. Calibratingmore than one transmit section at the same time reduces the total timeto calibrate all of the transmit sections included in a communicationssystem (or the subset of transmit sections included in thecommunications system to be calibrated).

Simultaneous calibration of a plurality of transmit sections uses aplurality of reference or calibration signals (e.g., orthogonal codebased signals), in which each orthogonal code based signal of theplurality of orthogonal code based signals has a different orthogonalityrelative to each other. For instance, if two transmit sections are to becalibrated simultaneously using the over-the-air calibration techniquedisclosed herein, then a first reference signal can be generated bywaveform generator 101 to transmit section 102 and a second referencesignal, having a different orthogonality from the first referencesignal, can be provided to another transmit section. The first andsecond reference signals are processed by respective transmit sections,the processing similar to that discussed above for the singlecalibration case. The first and second signals transmitted over-the-airare received by a calibration receive section, such as section 104. Thecalibration receive section performs correlations and determination ofcalibration factor for each of the transmit sections that transmittedthe first and second signals, similar to that discussed above for thesingle calibration case.

In the single calibration case, in which a single reference orcalibration signal is transmitted from a transmit section of interest,the calibration receive section is configured to generate correlationscomprising non-differential or single phase, time delay, and/oramplitude measurements or estimates. In the multi calibration case, inwhich more than one reference or calibration signals are simultaneouslytransmitted by more than one transmit section of interest, thecalibration receive section is configured to generate correlationscomprising non-differential/single phase, time delay, and/or amplitudemeasurements or estimates for each of the different reference signals ordifferential phase, time delay, and/or amplitude measurements orestimates between the different reference signals.

In some embodiments, a baseband section is optional in the calibrationreceive section 104.

FIG. 2 is an example illustration of a block diagram showingimplementation of an intra-chip calibration scheme in accordance withvarious aspects of the present disclosure. FIG. 2 shows animplementation in which more than one transmit section can besimultaneously calibrated. A single integrated circuit (IC) chip 200includes a waveform generator 201, a plurality of transmit sections 202,a calibration receive section 236, and a local oscillator 218. Thewaveform generator 201 is configured to generate first and secondreference signals or waveforms that comprise two different calibrationsignals (denoted as waveform 1 and waveform 2). First and secondreference signals differ from each other in at least orthogonality.Waveform generator 201 may be similar to waveform generator 101.

The plurality of transmit sections 202 comprises at least M number oftransmit sections, one for each of the M signal paths associated withthe M antenna elements supported by the chip 200. The M antenna elementsare antenna elements included in an antenna lattice of a phased arrayantenna. Each transmit section of the plurality of transmit sections 202is identical to each other. Each of the transmit sections 202 can besimilar to transmit section 102.

Calibration receive section 236 is similar to calibration receivesection 104. A calibration antenna element 234 is electrically coupledwith the calibration receive section 236. The calibration antennaelement 234 comprises an antenna element dedicated for calibration ofthe transmit sections such as one or more of transmit sections 202.Alternatively, calibration antenna element 234 can comprise an antennaelement switchable between use for calibration and for receiving normalor regular transmissions.

Local oscillator 218 is electrically coupled with each of the transmitsections 202 and the calibration receive section 236. Local oscillator218 is configured to generate and provide a common local oscillatorsignal (e.g., a common digital clock signal) to each of the transmitsections 202 and calibration receive section 236. Alternatively, localoscillator 218 can be located external to chip 200.

In some embodiments, first and second reference signals generated bywaveform generator 201 comprises the respective reference or calibrationsignals provided to two transmit sections of the plurality of transmitsections 202. For example, a transmit section 204 receives the firstreference signal or waveform (denoted as waveform 1), and a transmitsection 206 receives the second reference signal or waveform (denoted aswaveform 2). First and second reference signals comprise the calibrationsignals for respective transmit sections 204, 206.

Transmit section 204 electrically couples with an antenna element 220 ofthe M antenna elements. Transmit section 204 is associated with Txsignal path 1 of the M paths, and correspondingly, antenna element 220may be considered to be the i=1 antenna element, for i=1 to M. Transmitsection 206 electrically couples with an antenna element 222 of the Mantenna elements. Transmit section 206 is associated with Tx signal path2 of the M paths. The remaining transmit sections 202 likewiseelectrically couples with respective antenna elements, such as atransmit section 208 for path M associated with antenna element 228.Each of the M paths may include a PA located external to chip 200between the respective transmit section and associated antenna element.A bandpass filter may be included in each transmit section.

In some embodiments, each transmit section of the plurality of transmitsections 202 is configured to receive a data signal to be transmittedfrom a modem (e.g., data signal 150). The data signal comprises aregular signal, a normal signal, and/or the like that would betransmitted during regular or normal operation of the transmit section.

Transmit section 204 includes a baseband section 210 and a RF section212 similar to respective sections 106 and 112. Baseband section 210 isconfigured to encode the received data signal and combine or duplex withthe first reference signal (not encoded or processed as discussedabove), thereby generating a combined signal as the output of basebandsection 210. Alternatively, baseband section 210 can be configured tonot combine or duplex the encoded data signal with the first referencesignal, thereby providing the first reference signal as the output ofbaseband section 210. If no data signal is provided to transmit section204, then baseband section 210 passes through the first reference signalas the output of baseband section 210. The output of baseband section210 comprises the input to RF section 212. The RF section 212 performsRF processing on the known calibration signal (the output of basebandsection 210) suitable for antenna element 220 to transmit the knowncalibration signal. The known calibration signal is also provided tocorrelator 250. Alternatively, if the first reference signal is providedto correlator 250 by waveform generator 201, then providing the knowncalibration signal by transmit section 204 can be optional. A signalpathway 260 is shown representative of the traversal of the firstreference signal as discussed above.

Transmit section 206 includes a baseband section 214 and a RF section216 similar to respective sections 106 and 112. Baseband section 214 isconfigured to encode the received data signal and combine or duplex withthe second reference signal (not encoded or processed as discussedabove), thereby generating a combined signal as the output of basebandsection 214. Alternatively, baseband section 214 can be configured tonot combine or duplex the encoded data signal with the second referencesignal, thereby providing the second reference signal as the output ofbaseband section 214. If no data signal is provided to transmit section206, then baseband section 214 passes through the second referencesignal as the output of baseband section 214. The output of basebandsection 214 comprises the input to RF section 216. The RF section 216performs RF processing on the known calibration signal (the output ofbaseband section 214) suitable for antenna element 222 to transmit theknown calibration signal. The known calibration signal is also providedto correlator 248. Alternatively, if the second reference signal isprovided to correlator 248 by waveform generator 201, then providing theknown calibration signal by transmit section 206 can be optional. Asignal pathway 264 is shown representative of the traversal of thesecond reference signal as discussed above.

Remaining transmit sections 206 (for paths 3 to M) generate RF signalsfor respective inputted data signals and are radiated by respectiveantenna elements.

The RF signals radiated by the M antenna elements are detected by thecalibration antenna element 234, including RF signals associated withfirst and second reference signals from antenna elements 220 and 222(see respective signal pathways 262 and 266). The RF signals associatedwith first and second reference signals are transmitted at the same timeby respective antenna elements 220, 222.

The detected RF signals associated with first and second referencesignals are processed by calibration receive section 236 (e.g., downconverted to remove the carrier frequency, converted into a digitalsignal, etc.) and received at correlators 248, 250 included in Rx DFE246 (see signal pathway 268). The over-the-air received first referencesignal and the first reference signal (provided either as the output ofbaseband section 210 or from waveform generator 201) comprise the inputsto correlator 250. The over-the-air received second reference signal andthe second reference signal (provided either as the output of basebandsection 214 or from waveform generator 201) comprise the inputs tocorrelator 248.

Correlator 250 is configured to determine correlations between thereceived first reference signal and the first reference signal. Thedetermined correlations are provided to LMS engine 252 for use indetermination of a calibration factor for the transmit section 204. Thedetermined correlations comprise a quantification of the similaritybetween the received first reference signal and the first referencesignal.

Correlator 248 is configured to determine correlations between thereceived second reference signal and the second reference signal. Thedetermined correlations are provided to LMS engine 252 for use indetermination of a calibration factor for the transmit section 206. Thedetermined correlations comprise a quantification of the similaritybetween the received second reference signal and the second referencesignal.

The remaining transmit sections 202 can be calibrated employing asimilar calibration scheme.

FIG. 5 is an example illustration of a top view of an antenna lattice500 of a phased array antenna in accordance with various aspects of thepresent disclosure. A plurality of antenna element 502 is distributed toform the antenna lattice 500 having a particular antenna aperture. Mostof the antenna elements 502 comprise antenna elements associated withrespective transmit sections, such as transmit section 204. In additionto such transmitter antenna elements, a small subset of antenna elements502 can comprise calibration antenna elements. Antenna elements denotedas black squares comprise the calibration antenna elements (e.g.,calibration antenna elements 512, 504, 508).

In some embodiments, a single calibration antenna element is included ineach subset of the plurality of antenna elements 502 (e.g., each ofsubsets 506, 514, 510), in which the transmitter antenna elements 502 ofeach subset comprise the antenna elements that are within dynamic(receiving) range of the particular calibration antenna element. Forexample, calibration antenna element 504 is located to be within dynamic(receiving) range of the other antenna elements 502 within the subset506. Calibration antenna element 234 is an example of a singlecalibration antenna element within dynamic range of antenna elements220, 222, 226, and 228, thereby collectively forming a subset orcluster. Because calibration antenna element 234 is within dynamic range(e.g., able to sufficiently receive transmissions with sufficient SNR)of antenna elements associated with transmit sections within the samechip 200, both transmit and receive functions can be performed in thesame chip 200 to calibrate the transmit sections of chip 200.

It is contemplated that chip 200 may be configured to handle bothtransmitting and receiving of regular/normal/wanted signals. To thisend, chip 200 can further include a plurality of receive/receiversections associated with receipt and processing of normal/regular/wantedsignals in addition to the single calibration receive section 236associated with calibration-related operations and the plurality oftransmit sections 202.

FIG. 3 is an example illustration of a block diagram showingimplementation of an inter-chip calibration scheme for a same subset orcluster of antenna elements in accordance with various aspects of thepresent disclosure. Each of chips 300 and 320 is similar to chip 200.Antenna elements 310, 330, and 334 comprise antenna elements in the samesubset or cluster, such as the subset 506. Antenna element 310 isassociated with transmit section 308 included in the chip 300 (e.g.,chip 1), antenna element 330 is associated with transmit section 328included in the chip 320 (e.g., chip 2), and antenna element 334 isassociated with a calibration receive section 324 also included in chip320.

However, in contrast to FIG. 2 in which first and second referencesignals are transmitted and received by components included in the samechip 200, first reference signal transmitted via transmit section 308 ofchip 300 and antenna element 310 is detected by calibration receivesection 324 included in chip 320 and the second reference signaltransmitted using transmit section 328 of chip 320 and antenna element330 is detected by the calibration receive section 324 of chip 320. Thefirst reference signal transmitted by transmit section 308 is receivedby a calibration receive section located in a different chip from thetransmit section 308.

Calibration receive section 324 receives a first reference signal, via asignal pathway 344, from a waveform generator 321 located locally inchip 320. This first reference signal is the same as the first referencesignal (denoted as waveform 1) provided by waveform generator 301 totransmit section 308 for transmission.

Calibration receive section 324 receives a second reference signal, viaa signal pathway 342, from the baseband section of transmit section 328.Alternatively, the second reference signal can be provided by waveformgenerator 321 to calibration receive section 324, since waveformgenerator 321 is located in the same chip 320 as calibration receivesection 324.

Calibration receive section 324 then processes the received first andsecond reference signals and the (known) first and second referencesignals as discussed above in connection with FIG. 2 . The calibrationfactors determined by the LMS engine included in Rx DFE 324 are appliedto transmit sections 308, 328.

The remaining transmit sections 302, 322 are similarly calibrated byinjection of known reference/calibration signals, which may be receivedby a calibration receive section in the same or different chip from thetransmit sections undergoing calibration.

FIG. 4 is an example illustration of a block diagram showingimplementation of an inter-chip calibration scheme involving two subsetsor clusters of antenna elements in accordance with various aspects ofthe present disclosure. Each of chips 400 and 420 is similar to chip 200except chip 400 is associated with a first subset or cluster (denoted ascluster 1) of the antenna elements and chip 420 is associated with asecond subset or cluster (denoted as cluster 2) of the antenna elements,different from the first subset/cluster. For example, chip 400 may beelectrically coupled with at least some of the antenna elements 502included in subset 506 and chip 420 may be electrically coupled with atleast some of the antenna elements 502 included in subset 510.

Because chips 400 and 420 are associated with different antenna elementsubsets/clusters, all of the transmissions from antenna elements of thefirst subset/cluster may not be receivable or sufficiently receivable(due to weak signal strength, partial signal receipt, etc.) by antennaelements associated with a different subset/cluster such as the secondsubset/cluster. Likewise, transmissions from antenna elements of thesecond subset/cluster may not be fully receivable by antenna elements ofthe first subset/cluster.

In FIG. 4 , a first reference/calibration signal provided by a waveformgenerator 401 to a transmit section 408 is transmitted via an antennaelement 410. The transmitted signal is received by each of a calibrationreceive section 404 included in the same chip 400 as the transmitsection 408, via a calibration antenna element 405 (see signal pathway413), and also by a calibration receive section 424 included in the chip420, via a calibration antenna element 434 (see signal pathway 414).Either of the calibration receive sections 404, 424 can extract thereceived first reference signal from the rest of the signals received toperform calibration of transmit section 408. The first reference signalcan be provided to calibration receive section 404 by waveform generator401 (see signal pathway 418). The first reference signal (alone orcombined with a data signal) at the output of the baseband section oftransmit section 408 can be provided to calibration receive section 404by transmit section 408 (see signal pathway 416). Because calibrationreceive section 424 is located in a different chip from chip 400,waveform generator 421 included in chip 420 provides the first referencesignal to calibration receive section 424.

The waveform generators in the different chips are configured togenerate the same reference signals. And as discussed above, the outputof the baseband section of the transmit section of interest comprisesthe injected reference signal or the reference signal with the combineddata signal constituting noise relative to the reference signal. Thus,the reference signal provided to a calibration receive section is thesame regardless of whether it is provided by waveform generator 401,transmit section 408, waveform generator 421, and/or the like.

A second reference/calibration signal provided by waveform generator 421is the input to transmit section 428 included in chip 420. The secondreference signal is processed by transmit section 428 and transmittedvia antenna element 430. The transmitted second reference signal isreceived by calibration antenna element 434 and associated calibrationreceive section 424 (see signal pathway 442). However, calibrationantenna element 405 included in the first subset/cluster is unable to(fully) receive the transmitted second reference signal (see signalpathway 460). Accordingly, calibration receive section 424 is configuredto perform calibration determination for transmit section 428. Thesecond reference signal is provided to calibration receive section 424from one or both of the transmit section 428 (see signal pathway 448) orwaveform generator 421 (see signal pathway 450).

The remaining transmit sections 402, 422 are similarly calibrated byinjection of known reference/calibration signals, which may be receivedby a calibration receive section in the same or different chip from thetransmit section undergoing calibration.

In some embodiments, the transmit sections to be calibrated in FIGS. 1-4include digital beamformers (DBFs) in the baseband sections andcorrespondingly are configured to perform digital beamforming ofregular/normal signals to be transmitted.

FIG. 6A illustrates a block diagram showing example modules ofcorrelators and LMS engine configured to perform an over-the-aircalibration technique in accordance with various aspects of the presentdisclosure. In FIG. 6A, a correlation module 642, a difference module644, and an iteration module 646 are configured to perform computationsand processing associated with performance of over-the-air calibration.Correlation module 642 can be included in correlators shown in FIGS. 1-4(e.g., correlators 146, 148, etc.), and difference module 644 anditeration module 646 can be included in the LMS engines shown in FIGS.1-4 .

In a calibration receive section, the number of correlators, the numberof LMS engine, the locations of the correlators and LMS engine withinthe calibration receive section, and the different functionalitiesbetween the correlators and LMS engine discussed above are animplementation example and other configurations are within the scope ofthe present disclosure. For example, a single correlator can be includedin each calibration receive section rather than two, the functionalitiesof the correlators and LMS engine can be performed by a single processoror computational component, the correlators and LMS engine can belocated in the calibration receive section other than the Rx DFE, atleast a portion of the functionalities of the correlators and LMS enginecan be performed external to the calibration receive section, and/or thelike.

A calibration component 640 associated with a calibration receivesection includes modules 642-646. Consistent with the various possibleimplementations of the correlators and LMS engine, calibration component640 can be located within or external to calibration receive section.Calibration component 640 is also referred to as a calibration section.

In some embodiments, one or more of modules 642-646 (or a portionthereof) comprises one or more instructions embodied within a tangibleor non-transitory machine (e.g., computer) readable storage medium,which when executed by a machine causes the machine to perform theoperations described herein. Modules 642-646 (or a portion thereof) maybe stored local or remote from the calibration receive section. One ormore processors included in component 640 can be configured to executemodules 642-646 (or a portion thereof). In alternative embodiments, oneor more of modules 642-646 (or a portion thereof) may be implemented asfirmware or hardware such as, but not limited to, an applicationspecific integrated circuit (ASIC), programmable array logic (PAL),field programmable gate array (FPGA), and/or the like. In otherembodiments, one or more of modules 642-646 (or a portion thereof) maybe implemented as software while other of the modules 642-646 (or aportion thereof) may be implemented as firmware and/or hardware.

FIG. 6B illustrates a flow diagram showing a process 600 to calibrate atransmit section and associated antenna element using the over-the-aircalibration technique in accordance with various aspects of the presentdisclosure. At a block 602, a waveform generator (e.g., waveformgenerator 101) generates a reference calibration signal comprising anorthogonal code based signal. In some embodiments, the generatedreference signal comprises an orthogonal code based signal s Rx (t)having the following form.

s _(Rx)(t)=Cx(t−τ _(BB)−τ_(RF))e ^(2jπF)(t−τ _(RF))  Eq. (1)

where C=gain, τ_(BB)=baseband delay, τ_(RF)=RF delay (phase), and totaldelay τ=τ_(BB)+τ_(RF).

The generated reference signal is provided to the transmit section to becalibrated (e.g., transmit section 102). Such transmit section (alsoreferred to as the transmit section of interest) combines the referencesignal with the data signal in the baseband section (e.g., basebandsection 106), at a block 604. Block 604 is optional if transmit sectionis configured to ignore the received data signal and/or if no datasignal is provided to the transmit section of interest. The output ofthe transmit section's baseband section is the reference signal (notencoded as would be for the data signal) if block 604 is omitted or acombined signal comprising the reference signal (not encoded) and theencoded data signal. The encoded data signal component of the combinedsignal comprises noise relative to the reference signal component.

Next, at a block 606, the RF section (e.g., RF section 112) of thetransmit section of interest processes the baseband section output togenerate a RF signal of the reference signal or combined signal,whichever comprises the baseband section output. The antenna element(e.g., antenna element 124) electrically coupled with the RF sectiontransmits the RF signal over-the-air, at a block 610.

The transmitted RF signal is received by a calibration receive section(e.g., calibration receive section 104), at a block 612. In response,the calibration receive section processes the received RF signal(performing RF signal processing to down convert, convert to a digitalsignal, etc.) to generate a received reference signal, at a block 614.

The calibration receive section also receives the reference signal fromthe waveform generator and/or the baseband section output from thetransmit section of interest, via a wired connection, at a block 608.Which signal is provided to the calibration receive section can dependon which source is local (e.g., in the same chip or package) to thecalibration receive section. As discussed above, if, for example, thetransmit section of internet and the calibration receive section arelocated in different chips or packages, then the baseband section outputis not available to the calibration receive section. A waveformgenerator local to the calibration receive section can provide thereference signal to the calibration receive section. Note that thiswaveform generator is a different waveform generator from the one thatgenerated and provided the reference signal to the transmit section ofinterest.

In possession of both the reference signal/baseband section output andthe received reference signal, the calibration receive sectiondetermines correlations between the two signals, at a block 616. In someembodiments, the correlation module 642 associated with the calibrationreceive section is configured to determine the correlation between thereference signal/baseband section output and the received referencesignal. The correlation values or coefficients quantify the degree ofcorrelation between the two signals. The correlations provide an initialestimate of the gain C, RF delay (phase) τ_(RF), and total delay τ(collectively referred to as the initial gain and delay).

Next, at a block 618, the difference module 644 associated with thecalibration receive section is configured to determine a complex gain C′based on the initial gain and delay, in accordance with the followingequation.

C′=Ce^(−2jπFτ) ^(RF)   Eq. (2)

Difference module 644 calculates a difference D_(τ) using the initialgain and delay values and Equations 1 and 2 as follows:

D _(τ) =|C′x _(τ) −s _(Rx)|²  Eq. (3)

where s_(Rx), is the vector of the reference signal from block 608, andx_(τ) is the vector of the received reference signal (the transmittedreference signal received by calibration receive section and includingtotal delay τ). Difference D_(τ) is an estimated measure of the error inthe transmitted signal if particular gain and delay (compensation)values are applied. The goal is to minimize difference D_(τ) byparticular selection of gain and delay values. As will be describedbelow, acceptable gain and delay values can be determined by iterativelyestimating new gain and delay values based on the previous estimatedgain and delay values. Each new gain and delay values comprise smallchanges relative to the previous estimates using gradient andinterpolation techniques. Successive iterations of gain and delay valueestimates result in gain and delay values converging to particularvalues associated with a minimized difference D_(τ) (or the differencebeing within a pre-set value). Difference D_(τ) is also referred to asan error indicator, difference value, and/or the like.

If the difference value calculated at block 618 is equal to or less thana pre-set value (yes branch of block 620), then process 600 proceeds toblock 622. At block 622, the final gain and delay values—in this case,the initial gain and delay from block 616—comprise the particular valuesby which the transmit section of interest is calibrated. As will bedescribed below in connection with FIG. 7A, IQ gain and phasecompensator(s) and time delay filter(s) included in the transmit sectionare set in accordance with the final gain and delay values estimatedfrom injection of the reference signal to the transmit section ofinterest. The IQ gain and phase compensator(s) are configured topre-compensate for particular gain and RF delay (phase) offsets that arenow known to exist (and quantified) in signal transmissions performed bytransmit section of interest and associated antenna element. The timedelay filter(s) are configured to pre-compensate for particular basebanddelay offset now known to exist. The final estimated gain and delayvalues permit gain, baseband delay, and/or RF delay calibration.

If the difference value is greater than the pre-set value (no branch ofblock 620), then process 600 proceeds to block 624. At block 624, theiteration module 646 in conjunction with the difference module 644 areconfigured to determine a new estimate of the gain and delay valuesbased on the immediately previous gain and delay values. In the firstiteration, the immediately previous gain and delay are those from block616. In a given iteration, estimate a new x_(τ) (reference signaldelayed by value of τ) by interpolation of previous samples x₀ to x₁.Then calculate a new gain C_(new), as follows.

$\begin{matrix}{C_{new} = \frac{x_{\tau}^{H} \cdot s_{Rx}}{{❘x_{\tau}❘}^{2}}} & {{Eq}.(4)}\end{matrix}$

The new estimated delay τ is an update of the immediately previousestimated τ in accordance with a stochastic gradient.

With the new or latest gain and delay values determined, a newdifference value d(τ) can be calculated by the difference module 644, ata block 626, in accordance with the following equations.

C=(1−α).C _(old) +α.C _(new)  Eq. (5)

d(τ)=C.x _(τ) −s _(Rx)  Eq. (6)

where D_(τ) in Equation 3 is the square of the absolute value of errorsignal d(τ) of Equation 6. New delay value τ is calculated to minimizethe absolute value of error signal d(τ) using the following equationderived from a LMS algorithm.

τ=τ−μ.59 |d(τ)|²  Eq. (7)

The latest difference value is checked at block 620 to see if thedifference is now within the pre-set value, at block 620. If thedifference is greater than the pre-set value (no branch of block 620),then the next iteration is performed by returning to blocks 624-626 todetermine the next estimates of gain and delay. One or more iterationsoccur until the condition of block 620 is satisfied and process 600 canproceed to block 622.

In some embodiments, approximately 7-8 or fewer iterations can estimatesuitable gain and delay values for which the difference between thereference signal and the received reference signal will be within anacceptable range (e.g., the pre-set value of block 620). Such latest orfinal gain and delay values are the particular pre-compensation valuesto apply to regular signals to be transmitted in the transmit section ofinterest in order to proactively cancel out gain and delay offsets thatwill be introduced by the transmit section of interest and/or associatedantenna element. The final gain and delay values comprise a gain value,a baseband delay value, and/or a RF delay value (phase).

FIG. 7A illustrates an example block diagram showing gain and delaycompensator(s) included in a transmit section of interest in accordancewith various aspects of the present disclosure. In some embodiments, abaseband section 702 of the transmit section of interest includes,without limitation, IQ gain and phase compensator(s) 704, phaseshifter(s) 706, and time delay filter(s) 708. Each of IQ gain and phasecompensator(s) 704, phase shifter(s) 706, and time delay filter(s) 708can comprise one or more electrical components.

IQ gain and phase compensator(s) 704 are set in accordance with thefinal gain and RF delay (phase) values determined in process 600, atblock 622. Time delay filter(s) 708 are set in accordance with the finalbaseband delay value determined in process 600. Time delay filter(s) 708comprise baseband delay compensators. IQ gain and phase compensator(s)704 are also referred to as IQ gain and RF delay compensators. In someembodiments, additional gain and RF delay compensators and/or basebanddelay compensators may be included in the transmit section of interest,such as, within the RF section.

The RF section of the transmit section of interest can comprise aquadrature direct conversion transmitter (IQ) section, a quadraturedirect conversion transmitter, or the like. The components within the RFsection can define two parallel signal paths, a first set of componentsconfigured to process the I portion of a complex-valued signal and thesecond set of components configured to process the Q portion of thecomplex-valued signal. The IQ gain and phase compensator(s) 704 areappropriately configured to apply compensation and output compensated Iand Q portions of the complex-valued signal to the respective signalpaths defined in the RF section.

Returning to FIG. 6B, for simultaneous calibration of more than onetransmit sections of interest, such as discussed in connection withFIGS. 2-4 , process 600 can be performed in parallel using respectivefirst and second reference signals. As discussed above, the transmittedfirst and second reference signals can be received by the same ordifferent calibration receive sections. If the first transmittedreference signal is received by a first calibration receive section andthe second transmitted reference signal is received by a secondcalibration receive section, then the first calibration receive sectionperforms blocks 608, 612-626 for the transmit section of interest thattransmitted the first reference signal and the second calibrationreceived section performs blocks 608, 612-626 for the transmit sectionof interest that transmitted the second reference signal. Insimultaneous calibration of more than one transmit section of interest,the correlation module 642 at block 616 can be configured to calculatedifferential gain and delay measurements or estimates between the firstand second reference signals, instead of non-differential or absoluteestimates.

FIG. 8 is an example illustration of a block diagram showing IC chips800 and 810 and associated antenna elements in accordance with variousaspects of the present disclosure. Chip 800 is similar to chip 200, 300,320, 400, or 420 that includes a plurality of digital beamformingtransmit sections (also referred to as Tx DBFs) that electricallycouples with respective Tx antenna elements 802 and a single calibrationreceive section (also referred to as a calibration Rx) that electricallycouples with a calibration antenna element 808. Each of the Tx antennaelements 802 can include a PA 804 and an antenna 806. Although notshown, a PA can also be disposed between chip 800 and calibrationantenna element 808.

The calibration schemes described herein can also be performed forreceive sections that would be used to receive normal, regular, orwanted signals using a single dedicated calibration transmit sectionincluded in each chip. Continuing with the above nomenclature, insteadof Tx DBFs and calibration Rx as in chip 800, a chip 810 can include,respectively, a plurality of digital beamforming receive sections (alsoreferred to as Rx DBFs) and a single calibration transmit section (alsoreferred to as a calibration Tx) to calibrate the digital beamformingreceive sections. The plurality of digital beamforming receive sectionsis electrically coupled with respective Rx antenna elements 812 and thesingle calibration transmit section electrically couples with acalibration transmit antenna element 818. Each of the Rx antennaelements 812 includes a low noise amplifier (LNA) 814 and an antenna816. Although not shown, a LNA can also be disposed between chip 810 andcalibration antenna element 818.

One calibration antenna element associated with a calibration transmitsection is included in each subset/cluster of antenna elements of aphased array antenna associated with a receiver or receiver panel. Andas described above in connection with FIGS. 2-4 , intra- and/orinter-chip calibration schemes are also applicable for chip(s) includingRx DBFs and calibration Txs.

In an embodiment, an IC chip can include a calibration receive section,a calibration transmit section, a plurality of receive sections, aplurality of transmit sections, and a waveform generator.

FIG. 9 is an example illustration of a block diagram showingover-the-air calibration components in connection with receive sectioncalibration in accordance with various aspects of the presentdisclosure. In some embodiments, a calibration transmit section 902 iselectrically coupled to a calibration antenna element 914. Calibrationtransmit section 902 includes a Tx DFE 904, a DAC 906, a LPF 908, amixer 910, and a RF attenuator (Att) 912. DAC 906, LPF 908, and mixer910 are similar to respective DAC 116, LPF 118, and mixer 120.Calibration transmit section 902 is also referred to as a calibrationtransmitter, calibration Tx, and/or the like.

Tx DFE 904 is configured to perform one or more processing functionsrelating to channelization and/or sample rate conversion, as necessaryto ready inputted digital signals (e.g., the reference signal 952 andthe received reference signal from the receive section of interest) intoa format suitable for calibration-related determinations.

Tx DFE 904 includes a correlator 916 and a LMS engine 918. It isunderstood that although a single correlator 916 is shown, correlator916 can comprise more than one correlator. Correlator 916 is similar tocorrelators 146, 148, and LMS engine 918 is similar to LMS engine 160.Correlator 916 and LMS engine 160 can be located external to Tx DFE 904,external to calibration transmit section 902, and/or the like.

A waveform generator 901 is configured to generate and provide areference waveform or signal 952 to calibration transmit section 902.Waveform generator 901 is similar to waveform generator 101, andreference signal 952 is the same as reference waveform 152. Referencesignal 952 is also referred to as a calibration signal or waveform, areference calibration signal or waveform, and/or the like.

The reference signal 952 undergoes RF processing in the calibrationtransmit section 902. Namely, the reference signal 952 is converted froma digital signal into an analog signal by DAC 906, filtered by LPF 908,up converted to a carrier frequency via mixer 910, and attenuated by RFattenuator 912. The resulting outputted signal is referred to as a RFsignal. The RF signal is provided to calibration antenna element 914 tobe transmitted or radiated to a receive section 924 to be calibrated. APA or RF attenuator can be disposed between the output of calibrationtransmit section 902 and calibration antenna element 914, in someembodiments.

A signal pathway 920 denotes the propagation of the RF signal to receivesection 924. The RF signal is received by receive section 924 via anantenna element 922 electrically coupled thereto. Receive section 924includes a RF section 926 and a baseband section 940. RF section 926includes a LNA 928, mixer 930, LPF 932, an ADC 934, and an Rx DFE 936.Mixer 930, LPF 932, and ADC 934 are similar to respective mixer 138, LPF140, and ADC 142. Rx DFE 936 is configured to perform processing toready the signal for handoff to baseband section 940. RF section 926 isconfigured to process the received RF signal including down convertingto remove the carrier frequency, filtering, converting to a digitalsignal, perform amplification, and/or the like. The output of RF section926 comprises the received reference signal including potential gainand/or delay offsets introduced by antenna element 922 and/or receivesection 924. The output of RF section 926 is referred to as the receivedreference signal.

The output of RF section 926 can be provided to calibration transmitsection 902 via signal pathway 956. For regular signals that arereceived by receive section 924, after processing by RF section 926,such signal continues into baseband section 940 to undergo decoding byphase shifter(s) 942 and time delay filter(s) 944 to reconstitute orrecover the regular signal. For the received reference signal, suchsignal need not be provided to baseband section 940, as decoding is notnecessary.

A reference signal transmitted by calibration transmit section 902 (ananalog RF signal) propagates over-the-air (see signal pathway 960) to bereceived by antenna element 962 electrically coupled to receive section964. Receive section 964 is similar to receive section 924. Receivesection 964 includes a RF section 966 and a baseband section 980. RFsection 966 includes LNA 968, mixer 970, LPF 972, ADC 974, and Rx DFE976 similar to respective LNA 928, mixer 930, LPF 932, ADC 934, and RxDFE 936 of receive section 924. Baseband section 980 includes phaseshifter(s) 982 and time delay filter(s) 984 similar to respective phaseshifter(s) 942 and time delay filter(s) 944 of receive section 924.

The output of RF section 966 comprises the received reference signalincluding potential gain and/or delay offsets introduced by antennaelement 962 and/or receive section 964. The output of RF section 966 isreferred to as the received reference signal. Such output of RF section966 is provided to calibration transmit section 902 via signal pathway958. Signal pathways 956, 958 comprise wired connections (e.g.,conductive traces) between section 902 and respective sections 924, 964.

In some embodiments, over-the-air calibration of receive sections isperformed sequentially by calibration transmit section 902. A referencesignal is transmitted at a time t1 by calibration transmit section 902to be received by receive section 924. A reference signal is transmittedat a time t2, that is earlier or later than time t1, by calibrationtransmit section 902 to be received by receive section 964. Thereference signals transmitted at times t1 and t2 can be the same ordifferent from each other. For example, both reference signals can bethe first reference signal, both reference signals can be the secondreference signal, the reference signal at time t1 can be the firstreference signal and the reference signal at time t2 can be the secondreference signal, the reference signal at time t1 can be the secondreference signal and the reference signal at time t2 can be the firstreference signal, and/or the like.

In other embodiments, a single transmission of a reference signal bycalibration transmit section 902 can be received by more than onereceive section, such as both of receive sections 924 and 964. Each ofreceive sections 924, 964 performs RF processing on its received RFsignal and provides the output of its RF section (e.g., its receivedreference signal) to calibration transmit section 902.

Although calibration of two receive sections are discussed herein inconnection with FIG. 9 , it is understood that fewer or more than tworeceive sections can be calibrated by calibration transmit section 902.

The received reference signal provided by receive section 924 iscorrelated against the (originating) reference signal by correlator 916.The correlation is used by LMS engine 918 to determine gain and delayvalues appropriate to calibrate receive section 924, including one ormore iterations of estimated gain and delay values, as discussed hereinin connection with transmit section calibration. Likewise, the receivedreference signal provided by receive section 964 is correlated againstthe (originating) reference signal by correlator 916. LMS engine 918 isconfigured to determine gain and delay values with which to calibratereceive section 964.

A LNA can be disposed between antenna element 922 and receive section924, in some embodiments. A LNA can also be disposed between antennaelement 962 and receive section 964. Antenna elements 914, 922, and 962comprise part of a phased array antenna, such as inclusion in theantenna lattice 500.

In some embodiments, calibration transmit section 902 and the pluralityof receive sections to be calibrated (e.g., receive sections 924, 964)are included in the same IC chip or package or otherwise has a wiredconnection between each pair of a receive section to be calibrated andthe correlator/LMS engine associated with the calibration transmitsection 902.

In some embodiments, a baseband section is optional in the calibrationtransmit section 902. In some embodiments, the receive sections (e.g.,receive sections 924, 964) include digital beamformers (DBFs) in thebaseband sections (e.g., baseband sections 940, 980) and correspondinglyare configured to perform reverse digital beamforming of receivedsignals provided by respective RF sections (e.g., RF sections 926, 966)in order to recover the original data transmitted in the signals.

FIG. 10A illustrates a block diagram showing example modules ofcorrelator(s) and LMS engine configured to perform an over-the-aircalibration technique in accordance with various aspects of the presentdisclosure. A correlation module 1042, a difference module 1044, and aniteration module 1046 are configured to perform computations andprocessing associated with performance of over-the-air calibration ofreceive sections. Correlation module 1042 can be included in correlator916, and difference module 1044 and iteration module 1046 can beincluded in LMS engine 918. Correlation module 1042, difference module1044, and iteration module 1046 performs functions similar to respectivecorrelation module 642, difference module 644, and iteration module 646.

A calibration component 1040 associated with a calibration transmitsection includes modules 1042-1046. Consistent with the various possibleimplementations of the correlators and LMS engine, calibration component1040 can be located within or external to calibration transmit section.Calibration component 1040 is also referred to as a calibration section.

In some embodiments, one or more of modules 1042-1046 (or a portionthereof) comprises one or more instructions embodied within a tangibleor non-transitory machine (e.g., computer) readable storage medium,which when executed by a machine causes the machine to perform theoperations described herein. Modules 1042-1046 (or a portion thereof)may be stored local or remote from the calibration receive section. Oneor more processors included in component 1040 can be configured toexecute modules 1042-1046 (or a portion thereof). In alternativeembodiments, one or more of modules 1042-1046 (or a portion thereof) maybe implemented as firmware or hardware such as, but not limited to, anapplication specific integrated circuit (ASIC), programmable array logic(PAL), field programmable gate array (FPGA), and/or the like. In otherembodiments, one or more of modules 1042-1046 (or a portion thereof) maybe implemented as software while other of the modules 1042-1046 (or aportion thereof) may be implemented as firmware and/or hardware.

FIG. 10B illustrates a flow diagram showing a process 1000 to calibratea receive section and associated antenna element using the over-the-aircalibration technique in accordance with various aspects of the presentdisclosure. At a block 1002, a waveform generator (e.g. waveformgenerator 901) is configured to generate a reference signal. Block 1002is similar to block 602.

The generated reference signal is provided to a calibration transmitsection (e.g., calibration transmit section 902) to be converted into aRF signal for transmission, at a block 1004.

Next, at a block 1006, the RF signal is transmitted over-the-air by thecalibration transmit section. The transmission is received by a receivesection to be calibrated (the receive section of interest) (e.g.,receive section 924), at a block 1008.

The RF section of the receive section of interest processes the receivedRF signal to generate a received reference signal, at a block 1010. Thereceived reference signal comprises the RF section output. The RFsection output is provided to the calibration transmit section via awired connection, at a block 1012.

Next, at a block 1014, correlation module 1042 is configured to performcorrelations based on the reference signal and the RF section outputthat is the received reference signal. The correlations are used togenerate initial estimated gain and delay. Block 1014 is similar toblock 616 except the correlation module 1042 associated with thecalibration transmit section performs the determination.

Blocks 1016, 1018, 1020, 1024, and 1026 are similar to respective blocks616, 618, 620, 624, and 626 except the difference module 1044 anditeration module 1046 associated with the calibration transmit sectionare used instead of difference module 644 and iteration module 646. At ablock 1022, the receive section of interest is calibrated in accordancewith the final gain and delay estimates.

FIG. 7B illustrates an example block diagram showing gain and delaycompensator(s) included in a receive section of interest in accordancewith various aspects of the present disclosure. In some embodiments, abaseband section 712 of the receive section of interest includes,without limitation, IQ gain and phase compensator(s) 714, phaseshifter(s) 716, and time delay filter(s) 718. Each of IQ gain and phasecompensator(s) 714, phase shifter(s) 716, and time delay filter(s) 718can comprise one or more electrical components.

IQ gain and phase compensator(s) 714 are set in accordance with thefinal gain and RF delay (phase) values determined in process 1000, atblock 1022. Time delay filter(s) 718 are set in accordance with thefinal baseband delay value determined in process 1000. Time delayfilter(s) 718 comprise baseband delay compensators. IQ gain and phasecompensator(s) 714 are also referred to as IQ gain and RF delaycompensators. In some embodiments, additional gain and RF delaycompensators and/or baseband delay compensators may be included in thereceive section of interest, such as, within the RF section.

The RF section of the receive section of interest can comprise aquadrature direct conversion transmitter (IQ) section, a quadraturedirect conversion transmitter, or the like. The components within the RFsection can define two parallel signal paths, a first set of componentsconfigured to process the I portion of a complex-valued signal and thesecond set of components configured to process the Q portion of thecomplex-valued signal. The IQ gain and phase compensator(s) 714 areappropriately configured to receive I and Q portions of thecomplex-valued signal from the RF section, and then apply compensationto cancel out the gain and/or delay offset present in the I and Qportions of the complex-valued signal. Such compensated I and Q portionsof the complex-valued signal is then be decoded by phase shifter(s) 716and time delay filter(s) 718 to reconstitute the original datatransmitted. Absent the gain and delay offset compensation, the decodingperformed by phase shifter(s) 716 and time delay filter(s) 718 may notyield reconstitution of the original data transmitted.

Over-the-air calibration of antenna elements and associated circuitrysuch as, but not limited to, transmit sections and receive sections (orportions thereof) configured to perform baseband and RF processing ofsignals to be transmitted and received may occur at initial systemconfiguration, at system start up, periodically, continuously, on demandduring normal operation of the system, based on a trigger event (e.g.,temperature change above a threshold, operational life above athreshold, signal quality below a threshold, etc.), and/or the like.Over-the-air calibration of a transmit section facilitatespre-compensation of the signal to be transmitted by that transmitsection. Over-the-air calibration of a receive section facilitatespost-compensation of a signal received by that receive section. In thismanner, even a large number of antenna elements and associatedtransmission or receive circuitry can be calibrated and remaincalibrated over time.

In some embodiments, the transmit sections, receive sections,calibration transmit sections, calibration receive sections, associatedantenna elements, and waveform generators can be included in acommunications system, a wireless communications system, asatellite-based communications system, a terrestrial-basedcommunications system, a non-geostationary (NGO) satellitecommunications system, a low Earth orbit (LEO) satellite communicationssystem, one or more communication nodes of a communications system(e.g., satellites, user terminals associated with user devices,gateways, repeaters, base stations, etc.), and/or the like.

FIG. 11 illustrates a block diagram showing an example platform ordevice that can be implemented in at least a portion of the calibrationreceive section 104, 236, 304, 324, 404, and/or 424 and/or calibrationtransmit section 902 in accordance with various aspects of the presentdisclosure. Platform 1100 comprises at least a portion of any ofcorrelators 146, 148, 248, 250, or 916 and/or LMS engine 160, 252, or918. Platform 1100 as illustrated includes bus or other internalcommunication means 1115 for communicating information, and processor1110 coupled to bus 1115 for processing information. The platformfurther comprises random access memory (RAM) or other volatile storagedevice 1150 (alternatively referred to herein as main memory), coupledto bus 1115 for storing information and instructions to be executed byprocessor 1110. Main memory 1150 also may be used for storing temporaryvariables or other intermediate information during execution ofinstructions by processor 1110. Platform 1100 also comprises read onlymemory (ROM), static storage, or non-volatile storage device 1120coupled to bus 1115 for storing static information and instructions forprocessor 1110, and data storage device 1125 such as a magnetic disk,optical disk and its corresponding disk drive, or a portable storagedevice (e.g., a universal serial bus (USB) flash drive, a Secure Digital(SD) card). Data storage device 1125 is coupled to bus 1115 for storinginformation and instructions.

The processes explained above are described in terms of computersoftware and hardware. The techniques described may constitutemachine-executable instructions embodied within a tangible ornon-transitory machine (e.g., computer) readable storage medium, thatwhen executed by a machine will cause the machine to perform theoperations described. Additionally, the processes may be embodied withinhardware, such as an application specific integrated circuit (ASIC) orotherwise.

A tangible machine-readable storage medium includes any mechanism thatprovides (e.g., stores) information in a non-transitory form accessibleby a machine (e.g., a computer, network device, personal digitalassistant, manufacturing tool, any device with a set of one or moreprocessors, etc.). For example, a machine-readable storage mediumincludes recordable/non-recordable media (e.g., read only memory (ROM),random access memory (RAM), magnetic disk storage media, optical storagemedia, flash memory devices, etc.).

Examples of the devices, systems, and/or methods of various embodimentsare provided below. An embodiment of the devices, systems, and/ormethods can include any one or more, and any combination of, theexamples described below.

-   -   Example 1 is an apparatus in a communications system including a        transmit section including a first baseband section and a first        radio frequency (RF) section, wherein the transmit section is        configured to receive a calibration signal, the first RF section        is configured to generate a RF calibration signal based on the        calibration signal, and the RF calibration signal is void of        encoding by the first baseband section, and wherein the        calibration signal comprises an orthogonal code based signal;        and a receive section configured to receive the RF calibration        signal over-the-air, wherein the receive section includes a        second RF section and a calibration section, wherein the second        RF section is configured to generate a received calibration        signal based on the RF calibration signal, wherein the received        calibration signal and one or both of the calibration signal or        an output of the first baseband section associated with the RF        calibration signal comprise inputs to the calibration section,        and wherein the calibration section is configured to determine        one or more of gain, baseband delay, or RF delay compensation        values, based on the inputs, to calibrate the transmit section.    -   Example 2 includes the subject matter of any one or more of the        preceding Examples, and further includes a waveform generator        electrically coupled to the transmit section and configured to        generate and provide the calibration signal to the transmit        section and to the receive section, if the calibration signal is        to be provided to the receive section.    -   Example 3 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the calibration        signal comprises an orthogonal or code division multiple access        (CDMA) signal.    -   Example 4 includes the subject matter of any one or more of the        preceding Examples, and further includes a first antenna        electrically coupled to the transmit section and configured to        transmit the RF calibration signal; and a second antenna        electrically coupled to the receive section and configured to        receive the RF calibration signal, wherein calibration of the        transmit section comprises one or more of gain, baseband delay,        or RF delay offsets caused by one or both of the transmit        section or the first antenna.    -   Example 5 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the first and        second antennas are included in a phased array antenna.    -   Example 6 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the output of        the first baseband section associated with the RF calibration        signal comprises the calibration signal or a combination of the        calibration signal and an encoded data signal, wherein a data        signal comprises a regular signal to be transmitted by the        transmit section, and wherein the first baseband section is        configured to encode the data signal to generate the encoded        data signal and combine the encoded data signal with the        calibration signal.    -   Example 7 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the calibration        section includes a correlator and a least means square (LMS)        engine.    -   Example 8 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the calibration        section is configured to determine correlations based on the        received calibration signal and one of the calibration signal or        the output of the first baseband section associated with the RF        calibration signal, wherein the calibration section is        configured to determine initial gain and delay values based on        the correlations, and wherein the calibration section is        configured to determine a difference value based on the initial        gain and delay values.    -   Example 9 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein if the        difference value is within a pre-set value, then the initial        gain and delay values comprise the one or more gain, baseband        delay, or RF delay compensation values.    -   Example 10 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein if the        difference value is greater than a pre-set value, then the        calibration section is configured to iterate to determine new        gain and delay values based on the initial gain and delay        values, and wherein the calibration section is configured to        determine a new difference value based on the new gain and delay        values.    -   Example 11 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein if the new        difference value is within the pre-set value, then the new gain        and delay values comprise the one or more gain, baseband delay,        or RF delay compensation values.    -   Example 12 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein if the new        difference value is greater than the pre-set value, then the        calibration section is configured to iterate to determine        another new gain and delay values based on the new gain and        delay values, and wherein the calibration section is configured        to determine an another new difference value based on the        another new gain and delay values.    -   Example 13 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the transmit        section comprises a first transmit section, and further        including a second transmit section including a second baseband        section and a third RF section, wherein the second transmit        section is configured to receive a second calibration signal,        the second RF section is configured to generate a second RF        calibration signal based on the second calibration signal, and        the second RF calibration signal is void of encoding by the        second baseband section, and wherein the second calibration        signal differs from the calibration signal in at least        orthogonality, wherein the first and second transmit sections        simultaneously transmits the respective RF calibration signal        and the second RF calibration signal, wherein the receive        section is configured to receive the second RF calibration        signal over-the-air, wherein the receive section is configured        to generate a received second calibration signal based on the        second RF calibration signal.    -   Example 14 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the received        second calibration signal and one or both of the second        calibration signal or an output of the second baseband section        associated with the second RF calibration signal comprise second        inputs to the calibration section, and wherein the calibration        section is configured to determine one or more of second gain,        baseband delay, or and RF delay compensation values, based on        the second inputs, to calibrate the second transmit section.    -   Example 15 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the transmit        section and the receive section are included in a same        integrated circuit (IC) chip.    -   Example 16 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the transmit        section is included in a first integrated circuit (IC) chip and        the receive section is included in a second IC chip different        from the first IC chip.    -   Example 17 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the transmit        section includes one or more IQ gain and phase compensators and        time delay filters, and wherein the one or more IQ gain and        phase compensators is configured in accordance with the gain and        RF delay compensation values and the one or more time delay        filters is configured in accordance with the baseband delay        compensation value to pre-compensate for gain and delay offsets        associated with one or both of the transmit section or antenna        electrically coupled to the transmit section.    -   Example 18 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the transmit        section and the receive section are included in a communication        node of a satellite communications system.    -   Example 19 includes the subject matter of any one or more of the        preceding Examples, and further includes an apparatus included        in a communications system, the apparatus including a transmit        section including a first radio frequency (RF) section and a        calibration section, wherein the transmit section is configured        to receive a calibration signal, the first RF section is        configured to generate a RF calibration signal based on the        calibration signal, and wherein the calibration signal comprises        an orthogonal code based signal; and a receive section        configured to receive the RF calibration signal over-the-air,        wherein the receive section includes a second baseband section        and a second RF section, wherein the second RF section is        configured to generate a received calibration signal based on        the RF calibration signal, wherein the calibration signal and        the received calibration signal comprise inputs to the        calibration section, and wherein the calibration section is        configured to determine one or more of gain, baseband delay, or        RF delay compensation values, based on the inputs, to calibrate        the receive section.    -   Example 20 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the calibration        signal comprises a code division multiple access (CDMA) signal.    -   Example 21 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the receive        section includes one or more IQ gain and phase compensators and        time delay filters, and wherein the one or more IQ gain and        phase compensators is configured in accordance with the gain and        RF delay compensation values and the one or more time delay        filters is configured in accordance with the baseband delay        compensation value to post-compensate for gain and delay offsets        associated with one or both of the receive section or antenna        electrically coupled to the receive section.    -   Example 22 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein the second RF        section includes a down converter and a low noise amplifier        (LNA), and the first RF section includes an up converter and a        RF attenuator.    -   Example 23 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein a phase        accuracy associated with one or both of the receive section or        antenna electrically coupled to the receive section with        application of the RF delay compensation value is in a range of        a sub-picosecond.    -   Example 24 includes the subject matter of any one or more of the        preceding Examples, and further includes a waveform generator        configured to generate and provide the calibration signal to the        transmit section, and wherein the calibration section is        included in the first RF section.    -   Example 25 includes the subject matter of any one or more of the        preceding Examples, and further includes wherein determination        of the one or more gain, baseband delay, or RF delay        compensation values comprises iteratively estimating gain,        baseband delay, and RF delay values that correspond to a        minimization of an error factor between a calibration signal        representation and a received calibration signal representation        having estimated gain, baseband delay, and RF delay values of a        current iteration.

Although certain embodiments have been illustrated and described hereinfor purposes of description, a wide variety of alternate and/orequivalent embodiments or implementations calculated to achieve the samepurposes may be substituted for the embodiments shown and describedwithout departing from the scope of the present disclosure. Thisapplication is intended to cover any adaptations or variations of theembodiments discussed herein. Therefore, it is manifestly intended thatembodiments described herein be limited only by the claims.

What is claimed is:
 1. An apparatus included in a communications system,the apparatus comprising: a first baseband section configured to receivea calibration signal; a first RF section configured to generate a RFcalibration signal based on modulating the calibration signal, whereinthe calibration signal comprises an orthogonal code based signal; asecond RF section configured to receive the RF calibration signalover-the-air and configured to generate a received calibration signalbased on demodulating the RF calibration signal; a calibration section;a first antenna electrically coupled to the first RF section andconfigured to transmit the RF calibration signal; and a second antennaelectrically coupled to the second RF section and configured to receivethe RF calibration signal, wherein: the received calibration signal anda reference signal associated with the RF calibration signal compriseinputs to the calibration section; the calibration section is configuredto determine one or more of gain, baseband delay, or RF delaycompensation values, based on the inputs, to calibrate the first RFsection; and the second antenna is switchable between receiving the RFcalibration signal and transmitting an encoded data signal.
 2. Theapparatus of claim 1, further comprising a waveform generatorelectrically coupled to the first baseband section and configured togenerate and provide the calibration signal to the first basebandsection.
 3. The apparatus of claim 1, wherein the calibration signalcomprises a code division multiple access (CDMA) signal.
 4. Theapparatus of claim 1, wherein calibration of the first RF sectioncomprises one or more of gain, baseband delay, or RF delay offsetscaused by one or both of the first RF section or the first antenna. 5.The apparatus of claim 1, wherein the first and second antennas areincluded in a phased array antenna.
 6. The apparatus of claim 1, whereinthe reference signal associated with the RF calibration signal comprisesa combination of the calibration signal and an encoded data signal,wherein a data signal comprises a regular signal to be transmitted bythe first RF section, and wherein the first baseband section isconfigured to encode the data signal to generate the encoded data signaland combine the encoded data signal with the calibration signal.
 7. Theapparatus of claim 1, wherein the calibration section is configured todetermine correlations based on the received calibration signal and oneof the calibration signal or an output of the first baseband sectionassociated with the RF calibration signal, wherein the calibrationsection is configured to determine initial gain and delay values basedon the correlations, and wherein the calibration section is configuredto determine a difference value based on the initial gain and delayvalues.
 8. The apparatus of claim 7, wherein if the difference value iswithin a pre-set value, then the initial gain and delay values comprisethe one or more gain, baseband delay, or RF delay compensation values.9. The apparatus of claim 7, wherein if the difference value is greaterthan a pre-set value, then the calibration section is configured toiterate to determine new gain and delay values based on the initial gainand delay values, and wherein the calibration section is configured todetermine a new difference value based on the new gain and delay values.10. The apparatus of claim 9, wherein if the new difference value iswithin the pre-set value, then the new gain and delay values comprisethe one or more gain, baseband delay, or RF delay compensation values.11. The apparatus of claim 9, wherein if the new difference value isgreater than the pre-set value, then the calibration section isconfigured to iterate to determine another new gain and delay valuesbased on the new gain and delay values, and wherein the calibrationsection is configured to determine another new difference value based onthe another new gain and delay values.
 12. The apparatus of claim 1,further comprising: a second baseband section, wherein the secondbaseband section is configured to receive a second calibration signal;and a third RF section wherein the third RF section is configured togenerate a second RF calibration signal based on the second calibrationsignal, wherein: the second calibration signal differs from thecalibration signal in at least orthogonality; the first RF section andthe third RF section simultaneously transmit the RF calibration signaland the second RF calibration signal; and the second RF section isconfigured to receive the second RF calibration signal over-the-airsimultaneously with receiving the RF calibration signal, wherein thesecond RF section is configured to generate a received secondcalibration signal based on the second RF calibration signal.
 13. Theapparatus of claim 12, wherein the received second calibration signaland a second reference signal associated with the second RF calibrationsignal comprise second inputs to the calibration section, and whereinthe calibration section is configured to determine one or more of secondgain, baseband delay, or RF delay compensation values, based on thesecond inputs, to calibrate the second RF section.
 14. The apparatus ofclaim 1, wherein the first RF section includes one or more IQ gain andphase compensators and one or more time delay filters, and wherein theone or more IQ gain and phase compensators is configured in accordancewith the gain and RF delay compensation values and the one or more timedelay filters is configured in accordance with the baseband delaycompensation value to pre-compensate for gain and delay offsetsassociated with one or both of the first RF section or antennaelectrically coupled to the first RF section.
 15. The apparatus of claim1, wherein the reference signal comprises an output of the firstbaseband section.
 16. The apparatus of claim 1, wherein the referencesignal comprises the calibration signal.
 17. An apparatus included in acommunications system, the apparatus comprising: a baseband sectionconfigured to receive a calibration signal; an RF section configured togenerate a RF calibration signal based on modulating the calibrationsignal, wherein the calibration signal comprises an orthogonal codebased signal, wherein the RF calibration signal is void of encoding bythe baseband section; a receive section configured to receive the RFcalibration signal over-the-air, wherein the receive section includes asecond RF section, wherein the second RF section is configured togenerate a received calibration signal based on the RF calibrationsignal; and a calibration section, wherein: the received calibrationsignal and a reference signal associated with the RF calibration signalcomprise inputs to the calibration section; and the calibration sectionis configured to determine one or more of gain, baseband delay, or RFdelay compensation values, based on the inputs, to calibrate the RFsection.
 18. The apparatus of claim 17, further comprising: whereincalibration of the receive section comprises one or more of gain,baseband delay, or RF delay offsets caused by one or both of the secondRF section or an antenna coupled to the second RF section.
 19. Theapparatus of claim 18, wherein the RF calibration signal is void ofencoding by the baseband section.
 20. The apparatus of claim 17, whereinthe calibration signal comprises a code division multiple access (CDMA)signal.